Starting and operating circuit for high pressure arc lamps



June 2, 1959 F. BIRD 2,889,489

STARTING AND OPERATING CIRCUIT FOR HIGH PRESSURE ARC LAMPS Filed Oct. 15, 1957 INVENTOR.

Karl ATTORNEYS United States Patent OSTARTING AND OPERATING CIRCUIT FOR HIGH PRESSURE ARC LAMPS Lester F. Bird, Newark, N.J., assignor to Engelhard Industries, Inc., a corporation of New Jersey Thepresent invention relates to an operating circuit for electrical discharge lamps and more particularly to an operating circuit for the ignition and operation of high pressure gaseous discharge lamps.

While the ignition and operating circuit hereinafter described is advantageous for the ignition and operation of high pressure mercury vapor arc lamps, it is especially applicable for the ignition and operation of compact type are lamps containing an ionizable atmosphere of a rare gas, or rare gas and a vaporizable metal, at a pressure exceeding one atmosphere.

High pressure are lamps, e.g. compact arc lamps, are commonly connected to a source of usual line voltage, such as 120 volts line voltage, through a ballast adjusted to provide a lamp operating voltage of, for example, 75 volts. These lamps are advantageously started by means of high frequency pulses supplied from a pulse generating circuit connected across the lamp operating circuit on the lamp side of the ballast. In this location, the voltage initially supplied to the transformer energizing the pulse generating circuit is the line voltage. When the lamp is ignited, the voltage supplied to the starting transformer is automatically considerably reduced from the line supply value and becomes the lamp operating voltage, which voltage is insutfi'cient to maintain normal operation of the pulse generating circuit and discontinues the ignition pulses. I -Iowever, problems have resulted in the automatic operation of the ignition circuit because of the difiiculty in maintaining normal control of the ignition system at certain voltages which occur across the lamp. As long as the lamp voltage does not exceed about 50 volts, there is no difficulty with the ignition system. When the lamp voltages exceed 50 volts, e.g. 75 volts, it is difficult to prevent surges in voltage across the lamp from causing sporadic sparking across the spark gap of the pulse system. While this condition does not have any particular effect on the lamp, it causes radiation of radio waves from the ignition system, which can be detected by radio wave receiver means considerable distances from the location of the lamp equipment. Such condition is intolerable where absence of radio wave radiation is desirable. One remedy is to provide a manual switch means for closing the ignition circuit after lamp ignition, but this does not have the advantages of automatic operation. Another possibility is to provide a wider spacing of the spark gap to prevent the spark gap from breaking down under lamp voltages, but in such case the spark assumes a rough action and uncertain operation which does not always assure ignition of the lamp.

It is an object of this invention to provide a lamp ignition and operating system for high pressure arc lamps. It is another object of the present invention to provide a lamp operating system including an automatic high frequency pulse ignition circuit, wherein the ignition circuit voltage is automatically controlled and maintained at a value below a spark gap break-down voltage when ice the lamp is burning. Other objects and advantages will become apparent from the description hereinafter following and the drawing forming a part hereof.

The drawing is a schematic illustration of the lamp operating and ignition circuit according to the invention.

The invention deals with an ignition and operating system for high pressure arc lamps including a ballast in series with a high pressure are lamp, a pulse ignition circuit including a transformer therefor connected in the system between the ballast and lamp, and with a voltage control means for the ignition transformer particularly associated with the ballast, and whereby the transformer voltage is automatically controlled and maintained below a spark break-down of the pulse circuit.

The lamp contains spaced electrodes and an ionizable atmosphere of a rare gas, e.g. xenon, or a rare gas and a vaporizable metal, e.g. mercury, at a pressure exceeding atmospheric pressure.

Referring to the drawing, the system of the invention, comprises in combination a lamp operating circuit, an automatic lamp ignition circuit, and a voltage control circuit for the ignition circuit.

The. lamp operating circuit comprises supply lines 1 and 2 leading from a source of line voltage, e.g. 120 volts. One of the supply lines, e.g. line 1, is connected to a terminal 3 of a resistance or ballast 4. The other terminal 5 of ballast 4 is conected to a lead 6, which is connected to an electrode 7 of lamp 8. The other supplyline, e.g. line 2, is electrically connected to another electrode 9 of lamp 8. The ballast 4 is in series with the lamp and has an impedance so adjusted or selected that t the lamp,-when burning, will operate substantially at the rated lamp wattage.

The ignition circuit comprises an ignition transformer 10, having a primary winding 11 and secondary winding 12. Leads 13 and 14 are connected from the terminals of the ignition transformer secondary winding 12 to the terminals of primary winding 15 of a radio frequency transformer 16-. A radio frequency transformer secondary winding 17 is spaced from its primary winding 15 and connected into supply line 2 land in series with the lamp 8. A spark gap 18 is connected between the leads 13 and 14 and a capacitor 19 is connected into one of the leads 13 and 14. The ignition transformer 10, radio frequency transformer 16 and the intermediate spark gap 18 constitute components of the well known pulse type ignition circuits.

In order to isolate radio frequency from the line input circuit, a bypass lead 20 is connected across the supply line 2 and lead 6, with a by-pass condenser 21 connected into the by-pass lead to effect the isolation of the radio frequency.

If the primary winding 11 of ignition transformer 10 were connected directly across the supply line 2 and lead 6, the spark gap 18 would be subject to sporadic sparking when the lamp is in operation under lamp voltages exceeding 50 volts, which effect, as aforementioned, is intolerable under certain conditions.

According to the invention, the ignition circuit is provided with a voltage control circuit comprising a transformer 22 having a primary Winding 23 and secondary winding 24, with the primary winding 23 being connected across the terminals 3 and 5 of ballast 4 by means of leads 25 and 26. One terminal of the secondary winding 24 is electrically connected to the lead 6 by means of conductor or lead 27. The other terminal of secondary winding 24 is connected to a terminal of the primary winding 11 of the ignition transformer 10 by lead 28. The other terminal of primary winding 11 of the ignition transformer 10 is connected to the by-pass lead 20 through lead 29.

It is apparent from the drawing that the ignition trans- Patented June 2, 1959 assaesa;

3 former is electrically connected across lead 6' and supply line 2 between the ballast 4 and lamp 8 through the secondary winding 24 of the voltage control transformer 22.

When the input leads 1 and 2 are connected. to the line voltage, and before the lamp is ignited, full line voltage is delivered to the ignition transformer primary winding through the secondary winding of the voltage control transformer 22. There is a negligible voltage-drop across the ballast 4 and substantially no opposition to current to the ignition transformer-10 because, due to the lower resistance through ballast 4, the primary winding 23 is substantially short, circuited. Therefore, the ignition transformer 10 receives substantially full line voltageand operates the pulse system which establishes an arc across electrodes 7 and 9 and ignites the lamp. This is in contrast to the subsequent action of primary winding 23 in cancelling out at least a portion of the line voltage to transformer 10 when the lamp is ignited and the voltage drop across the ballast- 4 increases. When the lamp is ignited, the voltage across the primary 23 ofthe voltage control transformer 22 induces voltage in the secondary coil 24 thereof.

As soon as the larnp is ignited, the voltage, across lead 6 and supply line 2 between the ballast 4 and lamp 8 becomes lamp voltage and not line voltage because the lamp now operates under the lamp operating circuit through ballast 4, which conducts current when the lamp is ignited. Also, since voltage is now developed across the control transformer 22, which is in opposition to the line voltage, the voltage to the ignition transformer is reduced below the lamp operating voltage value. For example, the voltage now delivered to the ignition transformer is about 30 or more volts, below lamp operating voltages and far below any voltage that might cause sporadic arcing across the spark gap.

While the invention is described in connection with the specific system illustrated, modifications thereof are contemplated within the scope of the appended claims.

' Whatis claimed is:

1. An operating and ignition system for high pressure are lamps, comprising an arc lamp containing spaced electrodes and an ionizable atmosphere, leads connected to the electrodes, a ballast means in at least one of the leads in series with the lamp, a pulse type ignition circuit com.-

d prising an ignition transformer and a radio frequency transformer each having primary and secondary windings, conductors connecting the terminals of the secondary winding of the ignition transformer and the primary winding of the radio frequency transformer, a spark gap connected across said conductors, a capacitor in one of said conductors, the secondary winding of the radio frequency transformer being connected in one of the leads in series with the lamp, a voltage control means comprising atransformer having primary and secondary windings, the voltage control transformer primary winding being connected across terminals of the ballast means, a conductor means electrically connecting a terminal of the voltage control transformer secondary winding to one of said leads at a location between the ballast and the lamp, the other terminal of the voltage control secondary winding being connected to a terminal of the ignition transformer primary winding, the other terminal of" the ignition transformer primary winding being electrically connected to the other of said leads, and a by-passcapacitor connected across said input leads between the ballast and lamp.

2. An operating and ignition system for high pressure are lamps, comprising an arc lamp containing spaced electrodes and an ionizable atmosphere, leads connected to said electrodes, ballast means in at least one of the leads in series with the lamp, pulse type ignition means con nected in one of the leads in series with thelamp, means for energizing the ignition means, one conductor to the energizing means connected to one of the leads, another conductor to the energizing means connected-to the another of said leads at a location between theballast and lamp, atransformer comprising primary and secondary windings, the primary winding being connected across terminals of the ballast, the secondary winding being connected in series in said other lead to the energizing means, and a by-pass capacitor connected across said input leads between the ballast and lamp.

References Cited in the file of this patent UNITED STATES PATENTS Horstmann July 6, 1954 

